1. Field of the Invention
The present invention relates generally to input and pointing devices for data processing systems, and, more particularly, to cordless input and pointing devices such as mice, trackballs, computer pens, joysticks, and keyboards.
2. Background
With the advent of the information revolution, computers have found their way to most desks, be it in the office or at home. For the better part of the last two decades, most programs run by computers have been employing graphical user interfaces (GUIs) for inputting a substantial part of user-generated data and controls into the computers. Graphical user interfaces rely heavily on pointing devices—such as mice, trackballs, and touch pads—for most functions. For example, a computer operator can move a cursor on a computer display by manipulating the pointing device. Manipulation of the pointing device depends on the nature of the device. In case of a mouse, manipulation means sliding the mouse across a surface, such as a mouse pad. When the pointing device is a trackball, manipulation means rotating its ball in different directions. Finger-actuated buttons (switches) are typically provided on a pointing device for “clicking,” i.e., for selecting particular areas of the display, to cause the computer to perform the functions associated with the icons displayed in these areas.
A pointing device may be built into its host computer. More commonly, a pointing device is a device that is physically separate from its host computer. In the latter case, various methods can be employed to connect the pointing device to the computer through a cable. For example, the pointing device may plug into a standard RS 232 serial port of the computer through a serial cable. In another example, the pointing device may plug into a standard Universal Serial Bus (USB) port of the computer through a USB cable. Alternatively, the pointing device may plug into a proprietary interface port of the computer through a compatible proprietary cable. The cable connecting the pointing device to the host computer generally serves two purposes. First, it provides a link for the flow of data describing movements (manipulations) of the pointing device to the host computer. Second, the cable carries the electrical power necessary for the operation of the pointing device.
Cable connections between pointing devices and their corresponding host computers have a number of disadvantages. They add to the tangled webs of cables underneath a typical computer user's desk. They also limit the distance between a pointing device and a computer. And, of course, the extra cable on the desk adds to the clutter. Moreover, a cable used in one computer setup might not fit another setup. For example, a cable used to connect a mouse to a laptop (or notebook) computer—generally about two feet in length—will likely be too short for a desktop computer application. Thus, a computer user may need multiple pointing devices.
A cordless mouse obviates the inconveniences of the corded mouse: there is no need for a cord of any length, because a cordless mouse connects to the computer through a wireless link. The wireless link can be, for example, a radio frequency (RF) link, an optical link, an infrared link, or even an ultrasound link. Whatever the nature of this link, it enables a one- or two-way flow of data between the host computer and the mouse.
Recall, however, that the mouse cable serves two functions: (1) enabling the flow of data, and (2) supplying electrical power to the mouse. The wireless link can readily enable the flow of data, thereby fulfilling the first function, but it is not at all apparent how the wireless link can practically supply the electrical power to the mouse. The common solution in the art of wireless pointing devices is to provide a primary or secondary (rechargeable) cell within the wireless mouse to furnish the electrical power needed to operate the mouse. Thus, both functions formerly performed by a connecting cable are fulfilled in a wireless mouse. Unfortunately, this solution is not without its own deficiencies.
Of the two kinds of cells, that is primary and rechargeable, the latter appears to be a more economical and popular choice for cordless mice. In one implementation marketed under the name of GyroMouse, a cordless mouse can be used with a mouse pad, or it may be held in hand and used as a pointing device. The mouse uses rechargeable batteries, and needs to be placed in a special charging cradle for recharging.
With users who purchased a wireless rechargeable mouse with a charging cradle, forgetting to place the mouse in the cradle when leaving the office in the evening becomes a frequent event. When left outside the charging cradle, the mouse completely discharges overnight. Thus, the following morning the mouse has to be recharged before it can be used. Because placing the mouse in the charging cradle renders it inoperable as a pointing device, the mouse is useless while being recharged. Therefore, recharging, which typically takes several hours, renders the mouse useless during a significant portion of the following day. This nuisance leads many users to discontinue the use of the cordless mouse.
The charging problem disappears in the case of a mouse powered by primary cells, or by removable secondary cells. The frequent effort and expense necessitated by the need to replace the cells, however, do not make the use of replaceable cells a viable solution for many people.
Several attempts have been made to improve on the state of the art of wireless mice. For example, electrical power for a wireless mouse can be generated from the rotational motion of the ball of the mouse when the mouse slides across a surface.
In accordance with another attempt to improve on the art, an RF transmitter and a primary antenna are built into a mouse pad. The wireless mouse includes a secondary antenna for receiving the RF energy radiated by the primary antenna of the mouse pad. The RF energy thus received is converted into electrical energy for operating the wireless mouse. The host computer supplies the energy for the RF transmitter of the mouse pad.
Information relevant to attempts to improve on the art of wireless mice can also be found in U.S. Patent Application No. 20020118173; in Japanese Patent Application No. JP10283079; and in U.S. Pat. No. 6,445,379, issued to Liu et al. Although detailed analyses of the attempts described above are beyond the scope of the present document, each suffers from one or more of the following disadvantages:
Where the electrical energy for the operation of a mouse is derived from the mechanical movement of the mouse, it appears that excessive physical effort would be required to move the mouse in order to generate sufficient electrical power. Among other disadvantages, this approach is not at all applicable to optical devices, which are rapidly replacing the old ball-based mouse in popularity, and which have no ball to drive the generator that charges the battery.
As regards the method for coupling RF energy from a mouse pad to a wireless mouse, two speculative observations can be made. First, the efficiency of this method is quite low, because only a small portion of the radiated RF energy will be captured and used by the wireless mouse. Thus, the power drain from the host computer would be relatively high. Second, the deliberate radiation of RF energy might create unacceptable electromagnetic interference and, perhaps, alarm some health-conscious consumers.
A need thus exists for a pointing device with reduced power consumption characteristics during periods of nonuse. A further need exists for a pointing device that self-charges during the periods of its use as well as the periods of nonuse. Still another need exists for a pointing device that can be operated while being charged, or that can be operated without the need for a charged cell, and that overcomes the shortcomings of existing technologies.